Supply circuit for power amplifier drivers

ABSTRACT

An integrated power combiner is disclosed. The power combiner includes a first circular geometry primary winding having one or more inductive elements, such as an active winding with one or more driver stages. A circular geometry secondary winding is disposed adjacent to the first primary winding, such as an active winding with one or more driver stages. A second circular geometry primary winding is disposed adjacent to the secondary winding and has one or more inductive elements. One or more connections are provided between one or more of the inductive elements of the first circular geometry primary winding and one or more of the inductive elements of the second circular geometry primary winding.

RELATED APPLICATIONS

This application claims priority to U.S. Provisional application60/515,075, filed Oct. 28, 2003, which is hereby incorporated byreference for all purposes, and is related to U.S. patent applicationSer. No. 10/975,230, filed Oct. 24, 2004, entitled “Multi-primarydistributed active transformer oscillator power supply and control,” andU.S. patent application Ser. No. 10/975,316, filed Oct. 24, 2004,entitled “Multi-primary distributed active transformer amplifier powersupply and control,” each of which are commonly owned and assigned withthe present invention.

FIELD OF THE INVENTION

An integrated power amplifier is disclosed. In particular, a distributedactive transformer is disclosed for integrated power amplifiers withfully integrated single-band or multi-band integrated power amplifiers.

BACKGROUND OF THE INVENTION

Distributed active transformers (DATS) are known in the art. Inparticular, U.S. Pat. No. 6,737,948 discloses a circular geometry poweramplifier architecture that uses distributed active transformers in aloop configuration to amplify an input signal. Although the DAT of U.S.Pat. No. 6,737,948 provides many useful and novel features, additionaluseful and novel features are provided herein for use with DATs or inother suitable applications.

SUMMARY OF THE INVENTION

In accordance with the present invention, a system and method for DATpower supply and control are provided that overcome problems with DATpower supply and control.

In particular, a system and method for DAT power supply and control areprovided that accommodate dual primary windings.

In accordance with an exemplary embodiment of the present invention, anintegrated power combiner suitable for implementing amplifiers andoscillators is disclosed. The power combiner includes a first circulargeometry primary winding having one or more inductive elements, such asan active winding with one or more driver stages. A circular geometrysecondary winding is disposed adjacent to the first primary winding,such as an active winding with one or more driver stages. A secondcircular geometry primary winding is disposed adjacent to the secondarywinding and has one or more inductive elements. One or more connectionsare provided between one or more of the inductive elements of the firstcircular geometry primary winding and one or more of the inductiveelements of the second circular geometry primary winding.

The present invention provides many important technical advantages. Oneimportant technical advantage of the present invention is a system andmethod for DAT power supply and control that allows dual primarywindings to be used in a manner that minimizes losses due to phasedifferences between the primaries while allowing operation from a highersupply voltage, as well as other important technical advantages thatwill become apparent upon review of the specification and drawings.

Those skilled in the art will further appreciate the advantages andsuperior features of the invention together with other important aspectsthereof on reading the detailed description that follows in conjunctionwith the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 a is a diagram of a DAT in accordance with an exemplaryembodiment of the present invention;

FIG. 1 b is a diagram of an amplifying entity in accordance with anexemplary embodiment of the present invention;

FIG. 1 c is a diagram of an amplifier configuration for use as anamplifying entity with complementary outputs in accordance with anexemplary embodiment of the present invention;

FIG. 1 d is a diagram of a differential cascode amplifier for use as anamplifying entity in accordance with an exemplary embodiment of thepresent invention;

FIG. 1 e is a diagram of a cross-coupled oscillator for use as anamplifying entity in accordance with an exemplary embodiment of thepresent invention;

FIGS. 2 a through 2 g are diagrams of a DAT and associated amplifyingentities in accordance with an exemplary embodiment of the presentinvention;

FIG. 3 is a diagram of a DAT in accordance with an exemplary embodimentof the present invention;

FIG. 4 is a diagram of another DAT in accordance with an exemplaryembodiment of the present invention;

FIG. 5 is a diagram of a further DAT in accordance with an exemplaryembodiment of the present invention;

FIG. 6 is a diagram of another DAT in accordance with an exemplaryembodiment of the present invention;

FIG. 7 is a diagram of a DAT with offset amplifying entities (offsetDAT) in accordance with an exemplary embodiment of the presentinvention;

FIG. 8 is a diagram of an offset DAT in accordance with an exemplaryembodiment of the present invention;

FIG. 9 is a diagram of an offset DAT in accordance with an exemplaryembodiment of the present invention;

FIG. 10 is a diagram of concentric DAT in accordance with an exemplaryembodiment of the present invention;

FIG. 11 a is a diagram of a supply sharing circuit for driver circuitsin accordance with an exemplary embodiment of the present invention;

FIG. 11 b is a diagram of an alternative circuit to control regulationof the driver supply in accordance with an exemplary embodiment of thepresent invention;

FIG. 12 is a diagram of amplifiers in accordance with an exemplaryembodiment of the present invention;

FIGS. 13 a and 13 b are diagrams of a supply sharing circuit for drivercircuits in accordance with an exemplary embodiment of the presentinvention;

FIG. 14 is a diagram of a supply sharing circuit for driver circuits inaccordance with an exemplary embodiment of the present invention;

FIG. 15 is a diagram of a supply sharing circuit for driver circuits inaccordance with an exemplary embodiment of the present invention;

FIG. 16 a is a diagram of another supply sharing circuit for drivercircuits in accordance with an exemplary embodiment of the presentinvention;

FIG. 16 b is a diagram of an augmented supply sharing circuit for drivercircuits in accordance with an exemplary embodiment of the presentinvention;

FIG. 17 a is a diagram of a supply sharing circuit for driver circuitsin accordance with an exemplary embodiment of the present invention;

FIG. 17 b is a diagram of an alternative method and configuration toselect the series-supply path or the auxiliary paths;

FIG. 18 is a diagram of a supply sharing circuit for driver circuitssimilar to that shown in FIG. 17 a, except that the amplifiers each havea main input and an auxiliary input; and

FIG. 19 is a diagram of a supply sharing circuit for driver circuitssimilar to that shown in FIG. 18, except that the amplifier isimplemented using main input transistors.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the description that follows, like parts are marked throughout thespecification and drawings with the same reference numerals,respectively. The drawing figures might not be to scale, and certaincomponents can be shown in generalized or schematic form and identifiedby commercial designations in the interest of clarity and conciseness.

FIG. 1 a is a diagram of a DAT 100 in accordance with an exemplaryembodiment of the present invention. DAT 100 includes a first primarywinding 102 with inductive elements 102 a through 102 d, a secondprimary winding 104 with inductive elements 104 a through 104 d, and asecondary winding 106 placed so as to be magnetically coupled to bothprimary windings. Each inductive element can be a slab having arectangular shape, a trapezoidal shape, a stepped structure, a curvedstructure, or other suitable structures. Likewise, each inductiveelement can be identical to the other inductive elements, can matchopposite inductive elements, can be different from each other inductiveelement, or other suitable configurations of winding inductive elementscan be used, including but not limited to two or more integer numbers ofinductive elements and a corresponding number of drivers. Primarywinding 102 is driven by amplifying entities 108 a through 108 d, andprimary winding 104 is driven by amplifying entities 110 a through 110 dso that the inductive elements of the DAT can act as a power combiner.

FIG. 1 b is a diagram of an amplifying entity in accordance with anexemplary embodiment of the present invention. The amplifying entity ofFIG. 1 b can produce at least two output nodes 114 a and 114 b, in amanner so that the phase of the voltage produced at node 114 b issubstantially 180° out of phase with respect to the voltage produced atnode 114 a. The functions indicated in FIG. 1 b can be generallyrepresented by signal sources 112 a and 112 b which are connected to theoutputs 114 a and 114 b, respectively, so that the generated signals aresubstantially out of phase with each other and typically ofsubstantially equal amplitude. Furthermore, signal sources 112 a and 112b have an additional terminal 115 which is the common point relative towhich the two output signals are generated. This node can be used toconduct dc current to the amplifying entity.

FIG. 1 c is a diagram of an amplifier configuration for use as anamplifying entity with complementary outputs in accordance with anexemplary embodiment of the present invention. In this circuit,transistors 116 a and 116 b can be driven with control inputs (i.e.,signals applied to the MOSFET gates) which are substantially 180° out ofphase, thereby producing output voltages (i.e. outputs from the MOSFETdrains) which are similarly out of phase.

FIG. 1 d is a diagram of a differential cascode amplifier for use as anamplifying entity in accordance with an exemplary embodiment of thepresent invention. The differential cascode amplifier uses transistors122 a and 122 b with a common gate connection coupled to transistors 120a and 120 b, each of which can be a MOSFET as depicted or other suitabletransistors. In operation, the common gate voltage of transistors 122can be provided a bias voltage, while transistors 120 can be providedcomplementary drive signals representing the signal to be amplified. Thecascode amplifier can allow the use of a higher supply voltage comparedto the supply voltage that a non-cascode amplifier using the sametransistors can withstand. Furthermore, a cascode amplifier cantypically produce a higher power gain than a non-cascode amplifier usingthe same transistors.

FIG. 1 e is a diagram of a cross-coupled oscillator for use as anamplifying entity in accordance with an exemplary embodiment of thepresent invention. The control inputs of the two transistors 118 a and118 b are each connected to the output of the other. This configurationallows an oscillation to be developed which exists independently of anyinput signal, which by nature of the cross-coupling will generateoutputs that are substantially 180° out of phase with each other. Othersuitable configurations of amplifiers or oscillators can also oralternatively be employed to produce the function of FIG. 1 b, such asthat disclosed in U.S. application Ser. No. 10/687,679, entitledCircular Geometry Oscillators, filed Oct. 17, 2003, which is herebyincorporated by reference for all purposes.

Furthermore, the amplifying entities 108 and 110 of the DAT can ben-type transistor devices, p-type transistor devices, or suitablecombinations of both device polarities. The exemplary embodiments ofFIGS. 1 c, 1 d, and 1 e depict metal oxide semiconductor field effectdevices (MOSFETs), but other suitable devices can also or alternativelybe used. The amplifying entities can be implemented using bipolarjunction transistors (BJTs), heterojunction bipolar transistors (HBTs),high-electron-mobility field effect transistors (HEMTs), metalsemiconductor field effect transistors (MESFETs), or other suitablepower conversion devices such as transistors, or suitable combinationsof power conversion devices of multiple types.

A further example of a distributed active transformer is disclosed inco-pending and commonly owned U.S. patent application Ser. No.10/386,001, filed Mar. 11, 2003, which is hereby incorporated byreference for all purposes. Although secondary winding 106 is shown inFIG. 1, the secondary winding in other FIGURES disclosing otherexemplary embodiments may be removed for clarity.

Primary 102 and primary 104 can be connected at the amplifying entitiesas shown, at or near the location where the outputs of the amplifyingentities are connected to the DAT inductive elements. These connectionsmay be direct or may include suitable intervening components such asinductors or active devices such as to control current through theconnection or other suitable components. In this exemplary embodiment,the two primaries can be driven together with phase synchronizationwherein the phases of the voltage waveforms at the drivers of bothprimaries 102 and 104 are substantially the same. As such, the powerloss due to any phase difference between primaries 102 and 104 can beminimized or eliminated for all practical purposes, such that theelectro-motive-force (EMF) generated by both primaries 102 and 104 addsconstructively at all times and along all points of the primaries 102and 104. In accordance with this exemplary embodiment, this topology canreduce the effect on the power efficiency of any asymmetry that mayexist due to differences in components of DAT 100, such as differencesin inductive elements, drivers, connections, or other suitablecomponents. Such asymmetry can result in phase mismatch betweenprimaries and thus reduce the power efficiency of the DAT overtemperature and process variations. Furthermore, the connections betweenthe two primaries can assist in equalizing the amplitude of the voltagethat is produced on each primary, which may benefit by reducing theimbalance of voltage stresses on the various amplifying entities.Additionally, for some types of suitable amplifying entities, the dcvoltage of the DAT primaries may be affected by the properties andasymmetries of the DAT. By using the connections between the twoprimaries, the dc voltage of the two primaries can be made equal to oneanother, providing stability to the dc voltage of each primary.

FIGS. 2 a through 2 g are diagrams of a DAT 200 and associatedamplifying entities in accordance with an exemplary embodiment of thepresent invention. DAT 200 includes a first primary winding 202 withinductive elements 202 a through 202 d, a second primary winding 204with inductive elements 204 a through 204 d, and a secondary winding 206placed so as to be magnetically coupled to both primary windings.Primary winding 202 is driven by amplifying entities 208 a through 208d, and primary winding 204 is driven by amplifying entities 210 athrough 210 d so that the inductive elements of the DAT can act as apower combiner.

Furthermore, the common points of each amplifying entity connected toprimary 202 are provided a dc supply, while the amplifying entitiesconnected to primary 204 have their common points provided to aconductive path to ground. Connections are also made between theinductive elements of primaries 202 and 204 similar to those made in DAT100 which can additionally be used to conduct dc current from amplifyingentities 208 to amplifying entities 210. These connections can be madedirectly or through suitable intervening components which allow dccurrent to pass. For example, inductors can be used to allow dc currentto pass, or control circuits can be employed in these paths to controlthe amount of the supply current that is allowed to pass through theamplifying entities.

DAT 200 can be used to operate from a supply voltage which is greater,such as two times the supply voltage, than that which would be possiblefor a DAT where each amplifying entity is connected across the entiresupply. The mechanism for this benefit is demonstrated by the currentpaths, depicted as dashed lines 212 a and 212 b, from the supply to theground through two representative amplifying entities 208 d and 210 d.As can be seen, the current which flows into amplifying entity 208 dalso flows through amplifying entity 210 d before returning to ground.As such, the amplifying entities 208 d and 210 d share their dc supplycurrents in a series fashion. If amplifying entity 208 d is suitablymatched to amplifying entity 210 d, the dc voltage drop for eachamplifying entity for a given supply current can be made substantiallyequal. As a result, each amplifying entity will be subjected tosubstantially the same dc voltage as the other, which is approximatelyhalf of the voltage that the two together present to the supply. Forexample, if a 3.5V supply is applied, each amplifying entity can besubjected to a dc voltage of only 1.75V without placing additionalcomponents between the supply and the amplifying entities in order toreduce the voltage, which would typically result in a loss of dc power.

Although any type of power conversion device may be used, this methodand configuration can be beneficial if the amplifying devices connectedto primary 202 are composed primarily of p-type devices such as PMOStransistors or PNP bipolar transistors, and the amplifying entitiesconnected to primary 204 are implemented primarily from n-type devicessuch as NMOS transistors or NPN bipolar transistors. For instance, thecomplementary amplifiers of FIG. 2 b or FIG. 2 c could be selected foramplifying entities to be connected to primary 204. Similarly, anoscillator composed of n-type devices such as is depicted in FIG. 2 dcould be particularly suitable for the amplifying entities to beconnected to primary 204. The amplifiers of FIG. 2 e and FIG. 2 f andthe oscillator of FIG. 2 likewise represent amplifying entities that areparticularly suitable for connection to primary 202 By using p-typecircuits for the amplifying entities connected to the supply voltagesand n-type circuits for the amplifying entities connected to ground, thevarious bias signals and control signals, such as amplifier inputs, willtypically be at voltages which are greater than the supply and less thanground. This configuration reduces the difficulty of providing thesebias and control signals. Other suitable supply voltages can also oralternatively be applied in a similar manner, such as a positive and anegative supply voltage. Furthermore, other configurations of primariesmay be employed such as that the relative placement of the two primaries202 and 204 depicted in FIG. 2 may be such that primary 202 may belocated inside of primary 204 or other suitable configurations.

In one exemplary embodiment, the amplifying entities 208 a through 208 dand 210 a through 210 d can be arranged in a cross-differentialamplifier configuration, such as that disclosed in co-pending andcommonly owned U.S. patent application Ser. No. 10/385,777, filed Mar.11, 2003, and which is hereby incorporated by reference for allpurposes. This may be accomplished, for instance, by implementingamplifying entity 210 a in a fashion where it effectively operates astwo switches, implementing amplifying entity 208 a in a fashion where iteffectively operates as two switches, and supplying at least oneadditional inductor either in series with the dc supply connected toamplifying entity 208 a, in series with the ground connected toamplifying entity 210 a, or inductors in series with both connections.If this is done for the other three sets of amplifying entities, eachamplifying entity may be similarly made to operate in cross-differentialmode.

FIG. 3 is a diagram of DAT 300 in accordance with an exemplaryembodiment of the present invention. DAT 300 includes a first primarywinding 302 with inductive elements 302 a through 302 d, a secondprimary winding 304 with inductive elements 304 a through 304 d, and asecondary winding 306 placed so as to be magnetically coupled to bothprimary windings. Primary winding 302 is driven by amplifying entities308 a through 308 d, and primary winding 304 is driven by amplifyingentities 310 a through 310 d so that the inductive elements of the DATcan act as a power combiner. Furthermore, connections 312 a through 312d are provided to connect primaries 302 and 304 together. The point ofconnection on each primary may be made at or near a virtual ground whichtypically exists in DAT structures at or near the center of eachinductive element so as to reduce potential losses caused by ac currentsat the frequency of operation which might otherwise flow through thisconnection. These connections may be direct or may include suitableintervening components such as inductors or active devices such as tocontrol current through the connection or other suitable components.

The connections 312 can improve the performance of the DAT by equalizingthe dc voltages on the two primaries, by allowing current to be sharedbetween them in a similar fashion as if connections were to be made atthe amplifying elements' outputs, and in other manners. Furthermore,where any mismatch in the voltage stresses due to mismatch of the DATprimaries is tolerable, providing the connection near the virtual groundof the inductive elements can be preferable to providing connections atthe output of the amplifying elements because of the reduction of aclosses, as the connection between virtual grounds results in very littleac current through the connection, whereas the method of equalizing theac voltages on two DAT primaries by connecting the outputs of theiramplifying entities together relies on and can result in ac currentthrough the connection points. In addition, making connections betweenthe two primaries is often more easily accomplished since the virtualground points on a given primary are typically located away from theamplifying entities on the primary. Making this connection in an areathat is not near the amplifying entities reduces the difficulty ofrouting conductors that carry signals and currents, due to the largenumber of signals and high currents that are typically routed to andfrom the amplifying entities.

FIG. 4 is a diagram of DAT 400 in accordance with an exemplaryembodiment of the present invention. DAT 400 includes a first primarywinding 402 with inductive elements 402 a through 402 d, a secondprimary winding 404 with inductive elements 404 a through 404 d, and asecondary winding 406 placed so as to be magnetically coupled to bothprimary windings. Primary winding 402 is driven by amplifying entities408 a through 408 d, and primary winding 404 is driven by amplifyingentities 410 a through 410 d so that the inductive elements of the DATcan act as a power combiner. Furthermore, connections 412 a through 412d are provided to connect primaries 402 and 404 together. Theseconnections may be direct or may include suitable intervening componentssuch as inductors or active devices such as to control current throughthe connection or other suitable components. The point of connection oneach primary can be made at or near a virtual ground, which can exist inDAT structures at or near the center of each inductive element based onthe configuration of the DAT structures, so as to reduce potentiallosses caused by ac currents at the frequency of operation which mightotherwise flow through this connection.

Furthermore, the common point of each amplifying entity connected toprimary 402 is provided with a dc supply, while the amplifying entitiesconnected to primary 404 have their common points provided to aconductive path to ground. These connections can be made directly orthrough suitable intervening components which allow the current to pass.For instance, inductors can be used to allow dc current to pass, orcontrol circuits can be employed in these paths to control the amount ofthe supply current that is allowed to pass through the amplifyingentities.

A benefit of making the supply connections in this way is that the dccurrent consumed by the amplifying entities connected to primary 402 isshared with those connected to primary 404 in a similar fashion as DAT200. The shared current in this case can conduct through the DAT primaryinductive elements over the paths depicted by the dashed lines. If theamplifying entities are appropriately matched to one another, the dcvoltage drop across each amplifying entity can be limited, such as tonearly half of what it would be if the entire supply were to be appliedacross each amplifying entity individually. As a result, a higher supplyvoltage can be utilized without undue losses of power which can resultfrom other methods of reducing the dc voltage across the amplifyingentities. Other suitable supply voltages can also or alternatively beapplied in a similar manner, such as a positive and a negative supplyvoltage. Furthermore, other configurations of primaries may be employedsuch as that the relative placement of the two primaries 402 and 404depicted in FIG. 4 may be such that primary 402 may be located inside ofprimary 404 or other suitable configurations.

Relative to the system and method utilized for DAT 200 wherein theconnections are made at the outputs of the amplifying entities, thismethod and configuration of connecting at the virtual ground points canresult in lower ac losses due to the typically lower levels of accurrent which pass through the connection. It should be noted, though,that higher dc losses may result as the dc current between the variousamplifying entities is conducted through the parasitic resistance of theDAT inductive elements. Furthermore, the connection may not provide thebenefit of balancing the ac voltages on the two primaries at thefundamental frequency of operation. The exemplary amplifying entities ofFIGS. 2 b through 2 g can also or alternatively be used in conjunctionwith DAT 400 where suitable.

FIG. 5 is a diagram of DAT 500 in accordance with an exemplaryembodiment of the present invention. DAT 500 includes a first primarywinding 502 with inductive elements 502 a through 502 d, a secondprimary winding 504 with inductive elements 504 a through 504 d, and asecondary winding 506 placed so as to be magnetically coupled to bothprimary windings. Primary winding 502 is driven by amplifying entities508 a through 508 d, and primary winding 504 is driven by amplifyingentities 510 a through 510 d so that the inductive elements of the DATcan act as a power combiner. Furthermore, connections 512 a through 512d are provided to connect primaries 502 and 504 together. Connections512 a through 512 d can be made between the inductive elements ofprimary 502 and 504 in such a way that two connections are made betweenadjacent inductive elements of the two primaries at points which aresubstantially equidistant from the location of the virtual ground nearthe center of the inductive element to which the connection is made.These connections may be direct or may include suitable interveningcomponents such as inductors or active devices such as to controlcurrent through the connection or other suitable components.

This location of the connection points can help to achieve a trade-offbetween the relative advantages and disadvantages of forcedsynchronization such as is achieved using the connection points of DAT100 and connection at the virtual ground locations as in DAT 300. Therecan be less dc power loss compared to a center connection as the dccurrent path is shorter. There can be more equalization of ac voltagestresses compared to connection at the center connection at the virtualgrounds. Additionally, there can be less ac losses than a connection atthe outputs of the amplifying entities near the ends of the inductiveelements.

Furthermore, there can be more flexibility in the layout since theconnections are not required to be exactly at the point at which avirtual ground exists. In the event that the advantages of a connectionat the center near the virtual grounds is desired but becomes difficultdue to other considerations, two connections located symmetricallyequidistant from the virtual ground will typically be advantageousrelative to a single off-center connection, which can result inundesirable imbalances and typically higher second harmonic generation.

FIG. 6 is a diagram of DAT 600 in accordance with an exemplaryembodiment of the present invention. DAT 600 includes a first primarywinding 602 with inductive elements 602 a through 602 d, a secondprimary winding 604 with inductive elements 604 a through 604 d, and asecondary winding 606 placed so as to be magnetically coupled to bothprimary windings. Primary winding 602 is driven by amplifying entities608 a through 608 d, and primary winding 604 is driven by amplifyingentities 610 a through 610 d so that the inductive elements of the DATcan act as a power combiner. Furthermore, connections 612 a through 612d are provided to connect primaries 602 and 604 together. The point ofconnection on each primary can be made at or near a virtual ground,which can exist in DAT structures at or near the center of eachinductive element depending on the DAT configuration, so as to reducepotential losses caused by ac currents at the frequency of operationwhich might otherwise flow through this connection. These connectionsmay be direct or may include suitable intervening components such asinductors or active devices such as to control current through theconnection or other suitable components.

Furthermore, the common points of each amplifying entity connected toprimary 602 are provided to a dc supply, while the amplifying entitiesconnected to primary 604 have their common points provided to aconductive path to ground. These connections may be made directly orthrough suitable intervening components which allow the current to pass.For instance, inductors can be used to allow dc current to pass, orcontrol circuits can be employed in these paths to control the amount ofthe supply current that is allowed to pass through the amplifyingentities.

The benefits of making the supply connections in this configurationinclude that the dc current consumed by the amplifying entitiesconnected to primary 602 is shared with the amplifying entitiesconnected to primary 604 in a similar fashion as DAT 200. The sharedcurrent in this case can conduct through the DAT primary inductiveelements over the paths depicted by the dashed lines. If the amplifyingentities are appropriately matched to one another, the dc voltage dropacross each amplifying entity can be limited, such as to nearly half ofwhat it would be if the entire supply were to be applied across eachamplifying entity individually. As a result, a higher supply voltage canbe utilized without undue losses of power which can result from othermethods of reducing the dc voltage across the amplifying entities. Othersuitable supply voltages can also or alternatively be applied in asimilar manner, such as a positive and a negative supply voltage.Furthermore, other configurations of primaries may be employed such asthat the relative placement of the two primaries 602 and 604 depicted inFIG. 6 may be such that primary 602 may be located inside of primary 604or other suitable configurations.

Relative to the system and method utilized for DAT 200 wherein theconnections are made at the outputs of the amplifying entities, thismethod and configuration of connecting at the virtual ground points canresult in lower ac losses due to the typically lower levels of accurrent which pass through the connection. It should be noted, though,that higher dc losses may result as the dc current between the variousamplifying entities is conducted through the parasitic resistance of theDAT inductive elements. Furthermore, the connection may not provide thebenefit of balancing the ac voltages on the two primaries at thefundamental frequency of operation. The exemplary amplifying entities ofFIGS. 2 b through 2 g can also or alternatively be used in conjunctionwith DAT 600 where suitable.

FIG. 7 is a diagram of DAT 700 with offset amplifying entities (offsetDAT) in accordance with an exemplary embodiment of the presentinvention. The location of amplifying entities 708 a through 708 d onouter primary winding 702 are offset from the locations of amplifyingentities 710 a through 710 d on inner primary winding 704 at a suitableoffset, such as based on available space, to reduce losses, to optimizethe location of connections to V_(dd) or GND, to facilitate routing ofconductors for input and control signals to each amplifying entity, orfor other suitable purposes. The magnetic coupling between the inductiveelements 702 a through 702 d of the outer primary winding 702 and theinductive elements 704 a through 704 d of the inner primary winding 704to the secondary winding 706 and the loop currents determine the outputof secondary winding 706, thereby combining the outputs of theamplifying entities to be delivered to the load.

One beneficial offset configuration is where the amplifying entities 708a through 708 d are connected to primary 702 in proximity with thevirtual grounds 712 near the centers of the inductive elements ofprimary 704. This configuration can also result in the amplifyingentities 710 a through 710 d being connected to primary 704 in proximitywith the virtual grounds 714 located near the centers of the inductiveelements of primary 702. This connection can allow for advantageousconnections between the virtual grounds and the amplifying entities,e.g., where the dc voltage of inductive element 702 c is used to supplybias circuits connected to amplifying entity 710 c. Because theconnection point made to inductive element 702 c is at its virtualground, the connection can have minimal undesirable effects from accurrents induced in the connection, or from the coupling of ac voltageinto the connection.

Aside from enabling useful connections to the DAT elements, locating theamplifying entities near the virtual grounds as shown in DAT 700 canalso reduce capacitive coupling between the primaries and conductorscarrying control and bias lines which may have to be routed to theamplifying entity across the inductive element. For instance, conductorsfor control connections to amplifying entity 708 d may need to be routedto a circuit located in the center of DAT 700. By placing the virtualground of inductive element 704 c in proximity to amplifying entity 708c, the conductor for the signal can be routed through the virtualground, greatly reducing the undesirable capacitive coupling between theconductor for control line and the inductive element.

FIG. 8 is a diagram of offset DAT 800 in accordance with an exemplaryembodiment of the present invention. The location of amplifying entities808 a through 808 d on outer primary winding 802 are offset from thelocations of amplifying entities 810 a through 810 d on inner primarywinding 804 at a suitable offset, such as based on available space, toreduce losses, to optimize the location of connections to V_(dd) or GND,to facilitate routing of conductors for input and control signals toeach amplifying entity, or for other suitable purposes. The magneticcoupling between the inductive elements 802 a through 802 d of the cuterprimary winding 802 and the inductive elements 804 a through 804 d ofthe inner primary winding 804 to the secondary winding (not explicitlyshown) and the loop currents determine the output of the secondarywinding, thereby combining the outputs of the amplifying entities to bedelivered to the load.

DAT 800 also includes a dc supply voltage applied to the amplifyingentities 808 a through 808 d, such as at the virtual ground points ofthe inductive elements 802 or through some other suitable inductor orconducting element. A conductive path to ground is provided for each ofthe amplifying entities 810 a through 810 d, such as directly, through asuitable inductor, or through another conductive path. Additionally,each amplifying entity 808 a through 808 d has its common node connectedto or near to the virtual ground of the adjacent inductive element 804.

Implementing these dc connections in this manner can reduce the dcvoltage applied to each of the amplifying entities by sharing the dccurrents of amplifying entities 808 a through 808 d in series with theamplifying entities 810 a through 810 d along the path shown in dottedlines, so that each can be made to receive approximately half of thetotal supply voltage. Furthermore, the connections between amplifyingelements 808 a through 808 d and inductive elements 804 a through 804 dcan be made at the virtual grounds of the inductive elements, such thatthe connection can result in little additional ac losses or detrimentalac interference between primary 804 and amplifying entities 808 athrough 808 d. Other suitable supply voltages can also or alternativelybe applied in a similar manner, such as a positive and a negative supplyvoltage. Furthermore, other configurations of primaries may be employedsuch as that the relative placement of the two primaries 802 and 804depicted in FIG. 8 may be such that primary 802 may be located inside ofprimary 804 or other suitable configurations.

This technique is particularly advantageous in cases wherein it isdesirable to use only n-type devices such as NMOS transistors or NPNbipolar transistors, such as, for example, the amplifiers depicted inFIG. 2 b and FIG. 2 c and the oscillator of FIG. 2 d. Since bias andcontrol signals such as amplifier inputs must typically be applied atvoltage levels higher than the common voltage, DAT 800 allows amplifyingentities to be composed of n-type devices since all of the common nodesof amplifying entities 808 a through 808 d and 810 a through 810 d areat most approximately half the supply voltage, making generation ofhigher voltages less difficult than if voltages outside of the supplyrange were to be required. By way of counter-example, amplifying entity208 a in FIG. 2 a has its common point connected to the supply voltage,so that if this amplifying entity were to be implemented with n-typedevices, generation of appropriate bias and control voltages—which wouldtypically be even higher than the supply—might prove difficult.

Since n-type and p-type devices in any given technology or process canhave differences in performance, architectures such as DAT 800 can beused to enable use of only one of the device types, which can beadvantageous over architectures that are implemented using both types ofdevices. For example, in an exemplary sub-micron CMOS technology, NMOStransistors can have a higher cut-off frequency (T) or higher channelconductivity than PMOS transistors, such that DAT 800 with NMOStransistors can achieve higher power efficiency or operate at a higherfrequency than one employing both p-type and n-type devices. Thisarchitecture can be generalized to multiple levels of devices, which canbe useful such as for using low voltage devices to make a poweramplifier for a high voltage power supply or in other suitableapplications.

FIG. 9 is a diagram of offset DAT 900 in accordance with an exemplaryembodiment of the present invention. The location of amplifying entities908 a through 908 d on outer primary winding 902 is offset from thelocation of amplifying entities 910 a through 910 d on inner primarywinding 904 at a suitable offset, such as based on available space, toreduce losses, to optimize the location of connections to V_(dd) or GND,to facilitate routing of conductors for input and control signals toeach amplifying entity, or for other suitable purposes. The magneticcoupling between the inductive elements 902 a through 902 d of the outerprimary winding 902 and the inductive elements 904 a through 904 d ofthe inner primary winding 904 to the secondary winding (not explicitlyshown) and the loop currents determine the output of secondary winding,thereby combining the outputs of the amplifying entities to be deliveredto the load.

DAT 900 also includes a dc supply voltage applied to the common pointsof amplifying entities 908 a through 908 d, such as directly, through asuitable inductor, or through another conductive path. A conductive pathto or near to a virtual ground point on inductive elements 902 a through902 d is provided for each of the amplifying entities 910 a through 910d, such as directly, through a suitable inductor, or through anotherconductive path. Additionally, each inductive element 904 a through 904d is connected to ground, such as at the virtual ground points neartheir centers. These ground connections may be direct, through asuitable inductor, or through another conducting path.

Implementing these dc connections in this manner can reduce the dcvoltage applied to each of the amplifying entities by sharing the dccurrents of amplifying entities 908 a through 908 d in series with theamplifying entities 910 a through 910 d along the path shown in dottedlines, so that each may be made to receive approximately half of thetotal supply voltage. Furthermore, the connections between amplifyingelements 910 a through 910 d and inductive elements 902 a through 902 dcan be made at the virtual grounds of the inductive elements, such thatthe connection can result in little additional ac losses or detrimentalac interference between primary 902 and amplifying entities 910 athrough 910 d. Other suitable supply voltages can also or alternativelybe applied in a similar manner, such as a positive and a negative supplyvoltage. Furthermore, other configurations of primaries may be employedsuch as that the relative placement of the two primaries 902 and 904depicted in FIG. 9 may be such that primary 902 may be located inside ofprimary 904 or other suitable configurations.

Furthermore, using amplifying entities with p-type devices, such asthose shown in FIGS. 2 b through 2 d, may provide additional robustnessagainst device failure or allow operation at higher voltage levels asp-type devices can in many processes have the advantage of higherbreakdown voltage than similar n-type devices.

FIG. 10 is a diagram of concentric DAT 1000 in accordance with anexemplary embodiment of the present invention. Concentric DAT 1000includes DAT 1004 placed within the center area of DAT 1002, which canbe used to reduce the chip area required when two DATs are used, whilemaintaining the performance of each DAT. For instance, in applicationsrequiring output power to be generated at two different frequencies, alarger first DAT may be implemented to operate at the lower frequencywhile a smaller second DAT may be implemented to operate the higherfrequency and be located in the typically otherwise empty area locatedinside of the first DAT. This application is particularly suitable forconcentric DAT structures where the optimal size for a higher frequencyDAT is typically smaller than the optimum size for a lower frequencyone, so that each DAT may in principle reach nearly optimal performancewhile saving substantial area.

Alternatively, if operation at the same frequency is desired but at twodifferent power levels, a larger DAT may be designed which may be theoptimal size for that frequency to operate at the power level for whichefficiency is deemed more critical. Inside of this DAT, a smallerless-optimized DAT may be placed to enable operation at the second powerlevel with little or no increase in circuit area.

Likewise, this configuration can be expanded to encompass multiple DATsoperating at different frequencies and power levels, as well as usingside-by-side DATs or other suitable configurations. While the individualDATs of DAT 1000 can operate individually (one at a time), thisstructure can also be used to allow DAT 1002 and DAT 1004 to operatesimultaneously, such as at multiple frequencies, resulting in aconcurrent power amplifier.

FIG. 11 a is a diagram of a supply sharing circuit for driver circuitsin accordance with an exemplary embodiment of the present invention. Inthis supply sharing circuit, amplifiers 1100 and 1102 are configured tooperate in series with respect to dc supply 1105 so that supply currentflows through amplifier 1100, through a path represented by connection1104, and then through amplifier 1102 to ground. In this manner, eachamplifier can be subjected to a voltage that is less than the supplyvoltage 1105. Furthermore, if the amplifiers and their loads aresuitably matched, each amplifier can be operated with a dc voltageacross its supply terminals that is approximately half of the supplyvoltage 1105, so that the connection point 1104 has a dc voltage that isapproximately one half of the supply voltage 1105. Although for ease ofdescription the connection point 1104 is represented in FIG. 11 a as asingle connection which is separate from other connections havingdifferent functions, in many practical cases the connection path bywhich the supply current is shared between amplifiers 1100 and 1102 caninclude multiple paths. Furthermore, the connection path can be throughcircuit nodes which also serve a separate function, such as an output ora common point of a differential amplifier. By way of example, if thecircuit of FIG. 2 a is configured so that the amplifying entities areimplemented using amplifier circuits, the amplifiers 208 d and 210 dshare their supply currents in a series manner. The sharing is, however,through two separate paths denoted in the dashed lines, and furthermore,the points at which the amplifiers connect to these paths also serve thefunction of the amplifiers' outputs. The present invention can beadvantageously utilized for amplifier circuits which share dc supplycurrent in a suitable number of paths and also for circuits which sharecurrent through paths which include circuit nodes with additionalfunctions.

Driver circuits 1106 and 1108 provide input signals to amplifiers 1100and 1102 respectively. These driver circuits share their dc supplycurrents in series in a manner similar to amplifiers 1100 and 1102,through transistor 1110. If the driver circuits and their loads areappropriately matched to each other, the dc voltage drop across eachsupply connection can approximately equal the dc voltage drop across thesupply terminals of the other. Furthermore, by sharing their currents inseries, the total current provided from the supply 1105 to the drivercircuits can be substantially less than if the two drivers take currentfrom the supply separately in parallel current paths. Although FIG. 11 ashows only a single driver circuit providing input to each amplifier,the present invention can be advantageously applied in cases whereindriver circuits supply multiple inputs to amplifiers, such as byproviding differential or complementary signals. Furthermore, eachdriver circuit can comprise several circuits having various functionswhich have their supply terminals connected in parallel to each other.

A gate signal 1112 can be applied to transistor 1110 so as to controlthe total dc voltage to which the supply terminals of drivers 1106 and1108 are subjected. Transistor 1110 can control the supplies of bothdriver circuits simultaneously by appropriately restricting the currentpath between the driver circuits, thereby dropping varying amounts ofvoltage across its terminals. The driver circuits can utilize theremainder of the supply voltage 1105, each having approximately half ofthat part of supply voltage 1105 which transistor 1110 and any otherintervening circuitry is not dropping. A control voltage 1114 or othersuitable control circuit can be used to control the gate voltage 1112 toregulate the supply voltages available to driver circuits 1106 and 1108,such as to reduce sensitivity to changes or variation of supply voltage1105, to compensate for changes in temperature, or for other suitablepurposes.

In order to further stabilize the voltages applied to the supplyterminals of the drivers, capacitors 1116 and 1118 can be connectedacross the supply terminals of driver circuits 1106 and 1108respectively. These capacitors can reduce time-varying supply variationswhich occur too fast for the transistor 1110 and its control circuit tocompensate. Furthermore, these capacitors can reduce interference fromamplifiers 1100 and 1102 by reducing the amount of ac voltage induced inthe driver supplies at the frequency of the amplifier's operation and atharmonic frequencies.

In one exemplary embodiment, appropriate control signals are provided togate 1112 so as to regulate the driver circuit's supply voltages, toimplement transistor 1110 as an n-type transistor such as an NMOSdevice, and to supply the gate signal with a fixed voltage relative toground. In this manner, transistor 1110 can act as a source followerdevice, and so will tend to regulate the voltage at node 1119 relativeto ground, which is the dc supply voltage applied to driver circuit1108. If the driver circuit 1106 is appropriately matched to drivercircuit 1108, the supply voltage dropped by driver circuit 1106 may beapproximately the same as the supply voltage used by driver circuit 1108and so the dc supply voltage applied to driver circuit 1106 is similarlyregulated.

FIG. 11 b is a diagram of an alternative circuit to control regulationof the driver supply in accordance with an exemplary embodiment of thepresent invention. This circuit utilizes a servo mechanism withreference voltage 1124 and an error amplifier 1120, such as anoperational amplifier, which controls the gate of the regulatingtransistor 1122. The error amplifier receives reference voltage 1124 anda feedback voltage 1126. The amplifier can correct for variation involtage 1126 by sensing the difference between the voltage of node 1126relative to voltage 1124 and modifying the gate signal applied totransistor 1122 so as to set the voltages equal to each other.Alternatively, other feedback configurations can be used to set thevoltages to be proportional to each other or in other relations to eachother. Since node 1126 is also the supply voltage of driver circuit1130, the servo circuit serves to regulate the supply voltage applied todriver circuit 1130. Furthermore, if driver 1128 is appropriatelymatched to driver 1130, the supply voltage applied to driver 1128 can besimilarly regulated.

FIG. 12 is a diagram of a supply sharing circuit for driver circuits inaccordance with an exemplary embodiment of the present invention.Amplifier 1200 is implemented as a complementary amplifier similar tothe amplifier of FIG. 2 e, having transistors 1204 and 1206 which aredriven in a complementary fashion to produce complementary outputs attheir drains. Amplifier 1202 is implemented as a complementary amplifiersimilar to the amplifier of FIG. 2 b, having transistors 1208 and 1210which are driven in a complementary fashion to produce complementaryoutputs at their drains. The inputs of amplifier 1200 are provided by adriver circuit 1211 comprising driver 1214 and driver 1212, which drivethe gates of transistors 1204 and 1206, respectively. The inputs ofamplifier 1202 are provided by a driver circuit 1215 comprising driver1218 and driver 1216, which drive the gates of transistors 1208 and1210, respectively. Amplifiers 1200 and 1202 together provide fouroutput nodes 1228, which can be connected to an appropriate DAT such asin, for example, FIG. 2 a, FIG. 4, and FIG. 6. Alternatively the outputscan be combined in other suitable ways or used separately. Furthermore,amplifiers 1200 and 1202 can be implemented using other suitablecomplementary circuits, such as cascode amplifiers depicted in FIG. 2 cand FIG. 2 f or other suitable circuits.

FIGS. 13 a and 13 b are diagrams of a supply sharing circuit for drivercircuits in accordance with an exemplary embodiment of the presentinvention. Between the supply voltage 1309 and the supply connection ofamplifier 1300 located at node 1322 is inductance 1310, which may beparasitic or added for some function, such as to act as a choke. Due toac currents passing through inductor 1310, an ac voltage may begenerated on node 1322 superimposed on the dc voltage imposed by supply1309. An example of a typical voltage waveform 1324 which might occur isdepicted in FIG. 13 b.

This ac voltage ripple can cause problems in the supply circuits fordrivers 1306 and 1308 if precautions are not taken. Consider thewaveforms depicted in FIG. 13 b, depicting typical desirable waveformsin the case of an ac-corrupted supply for nodes 1322, 1314, and 1316which are the ac-corrupted supply, the supply for driver 1306, and thesupply for driver 1308, respectively. As noted before, waveform 1324consists of the desired dc supply voltage in addition to ac interferencesignals. Driver 1306 may require an approximately constant supply acrossits terminals, and so the desired waveform 1328 may be required to trackthe ac ripple of waveform 1324 so that the difference between 1328 and1324 is approximately constant. The supply applied to driver 1308,however, is referenced to ground and thus the voltage waveform 1326 at1316 should ideally be a constant voltage. Due to the ac voltage on node1314, it is possible that the time-varying voltage on node 1316 maybecome temporarily greater than the voltage on node 1314, possiblyresulting in the flow of current from node 1316 into node 1314. Forinstance, if the control circuit of FIG. 11 a were to be used,transistor 1110 would conduct current from source to drain during thesetimes, potentially resulting in voltage ripple on the two driversupplies. To reduce this effect, a rectifying device 1312 such as adiode or a diode-connected MOSFET can be placed in series with thecurrent path between the supply nodes 1314 and 1316 of the drivers, toeliminate or reduce any current from node 1316 to node 1314 during timeswhen the voltage at node 1314 becomes temporarily less than that at node1316.

Furthermore, capacitors 1318 and 1320 can be placed across the supplyterminals of drivers 1306 and 1308 respectively. In addition to supplyfiltering effects that these capacitors may provide, capacitors 1318 and1320 can also temporarily source the current to drivers 1306 and 1308during times when rectifying device 1312 is reverse biased so that thedriver currents cannot be taken from supply 1309. Thus, capacitors 1318and 1320 can accumulate and store charge during times when rectifyingdevice 1312 is forward biased, to be used as driver supply currentduring the times when the rectifying device 1312 is reverse biased.

FIG. 14 is a diagram of a supply sharing circuit for driver circuits inaccordance with an exemplary embodiment of the present invention.Between the supply voltage 1409 and the supply connection of amplifier1400 located at node 1422 is inductance 1410, which may be parasitic oradded for some function, such as to act as a choke. Due to ac currentspassing through inductor 1410, an ac voltage may be generated on node1422 superimposed on the dc voltage imposed by supply 1409. This acvoltage ripple may cause problems in the supply circuits for drivers1406 and 1408 if precautions are not taken, such as those describedabove in regards to the supply sharing circuit of FIG. 13.

To reduce the driver supply voltage which may result, more than onerectifying device may be placed in series between driver supply nodes1414 and 1416. Furthermore, switches 1424 can be used so that by closingthe appropriate switch or switches, one or more rectifying devices maybe bypassed. When this is done, the supply voltages applied to thedrivers will typically increase due to the reduced number of rectifierforward voltage drops since only the rectifying devices which are notbypassed drop this voltage during conduction. Thus by changing switchsettings, the driver supply voltages may be changed in discrete steps.Furthermore, by monitoring the voltage on node 1416, a control circuitcan be used to vary the number of bypassed rectifying devices so as tokeep the voltage at node 1416 close to a desired level. By doing this,variations in driver supply voltages such as due to variations in supplyvoltage 1409 or variations in the amount of induced ac voltage on node1422 can be compensated for.

FIG. 15 is a diagram of a supply sharing circuit for driver circuits inaccordance with an exemplary embodiment of the present invention.Between the supply voltage and the supply connection of amplifier 1500located at node 1522 is inductance 1510, which may be parasitic or addedfor some function, such as to act as a choke. Due to ac currents passingthrough inductor 1510, an ac voltage may be generated on node 1522superimposed on the dc voltage imposed by the supply. This ac voltageripple may cause problems in the supply circuits for drivers 1506 and1508 if precautions are not taken, such as those described above inregards to the supply sharing circuit of FIG. 13. In one exemplaryembodiment, the method and configuration described in FIG. 11 a can beadvantageously applied to provide the required voltage regulation usingtransistor 1512 and a suitable control voltage 1526 which may be a fixedvoltage or be generated by a feedback circuit or some other suitablecircuit.

FIG. 16 a is a diagram of a supply sharing circuit for driver circuitsin accordance with an exemplary embodiment of the present invention. Inthis exemplary embodiment, the supply voltage 1604 for the driver andamplifier combination has been generated from a higher voltage supply1603 using transistor 1607. Transistor 1607 can be used to implementpower control, such as by modifying the output power created by 1600 and1602, by changing the voltage 1604, and in other suitable manners.

One potential issue with reducing the output power by reducing thevoltage at internal supply node 1604 is that the driver circuits mayhave insufficient supply voltage to function correctly at some lowerrange of power levels. By way of example, if drivers 1606 and 1608 wereto require at least 1V across each of their supply nodes to functioncorrectly, the drivers would be unable to function with less than 2V onnode 1604. To reduce this effect, an auxiliary supply path 1620 can beimplemented which can be activated to provide supply current to drivercircuit 1608 directly from supply 1603, in certain situations such aswhen the voltage at node 1604 is insufficient to adequately supplydrivers 1606 and 1608.

Auxiliary path 1620 consists of NMOS transistor 1622 to which anappropriate gate voltage 1624 is applied so as to regulate the supplyvoltage 1612 of driver circuit 1608 during times when the auxiliary pathis active. In this manner, transistor 1622 can act as a source followerdevice, and can regulate the voltage at node 1612 relative to ground. Ifthe auxiliary path is inactive, the voltage can be set to a sufficientlylow voltage to turn transistor 1622 completely off. Alternatively, thegate voltage 1624 can be set so that the auxiliary path will regulate toa voltage on node 1612 which is less than the voltage produced by theseries-supply path when there is sufficient voltage for that path to becorrectly functioning. In this case, transistor 1622 can reduce itscurrent or even turn off completely when the series-supply path isactive without any change in gate voltage 1624 being necessary, such asby reducing the gate-source voltage on transistor 1622 when the node1612 is at the higher voltage produced by the series-supply circuit.

FIG. 16 b is a diagram of an augmented supply sharing circuit for drivercircuits in accordance with an exemplary embodiment of the presentinvention. In this circuit, inductance 1628 (which can be a parasiticinductance or have a selected value) can be used to create an ac voltageon supply node 1632. This ac voltage can potentially compromise correctfunctioning of the auxiliary supply path in cases where the voltage onnode 1632 is temporarily less than the voltage on node 1630. To reduceor eliminate this effect, a rectifying device 1633 such as a diode or adiode-connected transistor can be placed in series with the auxiliarycurrent path to reduce or eliminate this reverse current. Capacitor 1634can be used to source supply current into driver 1636 during the timeswherein the rectifying device 1633 is reverse biased.

FIG. 17 a is a diagram of a supply sharing circuit for driver circuitsin accordance with an exemplary embodiment of the present invention. Inthis exemplary embodiment, the supply voltage for the driver andamplifier combination consisting of the voltage difference between nodes1718 and 1720 has been generated from a higher voltage supply usingtransistor 1710 and supply transistor 1712. Transistors 1710 and 1712can be used to implement power control, such as by modifying the outputpower created by 1700 and 1702, by changing the voltages at 1718 or1720, and in other suitable manners. Transistors 1710 and 1712 each dropsupply voltage—typically nearly equal to each other—to reduce the outputpower to provide power control function. This can reduce the voltagebetween 1718 and 1720 such as to perform power control function. In somesituations, such as when transistors 1710 and 1712 are droppingrelatively large amounts of voltage, the series-supply path may nolonger be able to supply the drivers as in the supply sharing circuitfor driver circuits shown in FIG. 16 a. Two auxiliary paths are used tosupply the two drivers in these situations, and rectifying devices 1738and 1740 may be used to reduce the effects of any ac corruption of thesupplies, such inductor bounce.

FIG. 17 b is a diagram of an alternative method and configuration toselect the series-supply path or the auxiliary paths. In this exemplaryembodiment, additional switches 1742 and 1744 are placed in series withthe auxiliary supply paths and switch 1746 is placed in series with theseries-supply path. By closing switch 1746 and opening switches 1742 and1744, the series-supply path may be selected. To select the auxiliarysupplies, switches 1742 and 1744 may be closed while switch 1746 isopened.

FIG. 18 is a diagram of a supply sharing circuit for driver circuitssimilar to that shown in FIG. 17 a, except that the amplifiers 1800 and1802 each have a main input and an auxiliary input. The main inputs areprovided inputs from drivers 1806 and 1808 taking their supply currentsfrom a series supply path which may be active when the output power ishigh, such as when the voltage across 1807 and 1809 is sufficient tosupply the series-supply current path. The auxiliary inputs are providedinputs from drivers 1810 and 1812 which take their supply currents fromauxiliary supply paths. The supply sharing circuit of FIG. 18 can beoperated with both the main and auxiliary paths activated, except at lowpower when the main path naturally fails, or so that the auxiliary pathsare turned off at high power. Note that diodes 1826 and 1828 can be usedto avoid problems with ac on the supply nodes 1807 and 1809, such aswhen an inductor is used in series with the supply.

FIG. 19 is a diagram of a supply sharing circuit for driver circuitssimilar to that shown in FIG. 18 with exemplary amplifiers 1900 and 1902having main and auxiliary inputs. Amplifier 1900 is implemented usingmain input transistors 1904 a and 1904 b. Input transistor 1904 areceives input signals from main driver circuit 1916. Auxiliary inputtransistor 1906 a receives input signals from auxiliary driver circuitssuch as driver 1918. The driver circuits for input transistors 1904 band 1906 b are not explicitly shown, but can be configured in a similarmanner. The drains of input transistors 1904 a and 1906 a connect to thesource of cascode transistor 1908 a while the drains of inputtransistors 1904 b and 1906 b connect to the source of cascodetransistor 1908 b. A similar configuration can be used for amplifier1902. Main drivers 1916 and 1920 can provide input signals to amplifiers1900 and 1902 in situations where their series supply path hassufficient voltage to operate. When the series supply path hasinsufficient voltage, such as when transistors 1924 and 1926 aredropping relatively large voltages, the outputs of the main drivers maybe unable to provide appropriate signals to transistors 1904 and 1910,such as if the signals are too weak or at the wrong dc bias point.Auxiliary drivers 1916 and 1920 can be used to drive auxiliary inputtransistors 1906 and 1910, so that the auxiliary transistors can provideall or most of the control of the output gain of amplifiers 1900 and1902.

The drains of cascode transistors 1908 and 1914 form the outputs 1940 ofthe amplifiers which may be connected to an appropriate DAT such as in,for example, FIG. 2 a, FIG. 4, and FIG. 6. Alternatively the outputs canbe combined in other suitable ways or used separately. Furthermore,amplifiers 1900 and 1902 can be implemented using other suitablecomplementary circuits, such as by eliminating cascode transistors 1908and 1914 and using the connected the drains of transistors 1904 and 1906and the connected drains of transistors 1910 and 1912 as outputsdirectly, or other suitable circuits.

Although exemplary embodiments of a system and method of the presentinvention have been described in detail herein, those skilled in the artwill also recognize that various substitutions and modifications can bemade to the systems and methods without departing from the scope andspirit of the appended claims.

1. An amplifier comprising: a first driver stage having a first supplyterminal, a second supply terminal, and an output terminal coupled to aninput of a first amplifier stage; a second driver stage having a firstsupply terminal, a second supply terminal, and an output terminalcoupled to an input of a second amplifier stage; a transistor having agate, a source, and a drain, wherein: the first driver is provided afirst dc supply voltage at its first supply terminal; the second driveris provided a second dc supply at its first supply terminal; aconducting path which includes the transistor is provided so that supplycurrent may conduct between the second terminals of the first and seconddriver stages; and a voltage is applied to the gate of the transistor soas to control a voltage of the second supply terminal of the firstdriver.
 2. The amplifier of claim 1 further comprising a rectifyingdevice placed in series with the drain of the MOSFET transistor.
 3. Theamplifier of claim 1 further comprising a plurality of rectifyingdevices placed in series with the drain of the MOSFET transistor.
 4. Theamplifier of claim 1 further comprising: a plurality of rectifyingdevices placed in series with the drain of the MOSFET transistor; aplurality of switches, where each switch is in parallel with one of therectifying devices; and wherein the number of rectifying devices inseries with the drain of the MOSFET transistor can be controlled byclosing one or more of the plurality of switches.
 5. The amplifier ofclaim 1 wherein the amplifier is used to drive a distributed activetransformer.
 6. A amplifier, comprising: a first driver stage having afirst supply terminal, a second supply terminal and an output terminal;a second driver stage having a first supply terminal, a second supplyterminal and an output terminal; the output terminal of the first driverstage is coupled to an input of a first amplifying entity; the outputterminal of the second driver stage is coupled to an input of a secondamplifying; the first supply terminal of the first driver is connectedto a common node of the first amplifying entity; the first supplyterminal of the second driver is connected to a common node of thesecond amplifying entity; and a dc current flows from the second supplyterminal of the first driver to the second supply terminal of the seconddriver.
 7. The amplifier of claim 6 further comprising a rectifyingdevice placed in series between the second supply terminals of the firstand second drivers.
 8. The amplifier of claim 7, further comprising acapacitor connected in series between the first and second supplyterminals of the first driver.
 9. The amplifier of claim 7, furthercomprising a switch configured to controllably bypass the rectifyingdevice.
 10. The amplifier of claim 6 further comprising a plurality ofrectifying devices coupled in series between the second supply terminalsof the first and second drivers.
 11. The amplifier of claim 10 furthercomprising a capacitor coupled to the first and second supply terminalsof the first driver.
 12. The amplifier of claim 10 further comprising aswitch configured to selectively bypass one or more of the rectifyingdevices.
 13. The amplifier of claim 6 further comprising: a MOSFETdevice having a gate, a source, and a drain; the source of the MOSFET isconnected to the second supply terminal of the first driver; and avoltage applied to the gate of the MOSFET controls the voltage on thesecond supply terminal of the first driver.
 14. The amplifier of claim13 further comprising a rectifying device in series between the secondsupply terminals of the first and second drivers.
 15. The amplifier ofclaim 6 further comprising an auxiliary current path from a supplyvoltage to the second supply terminal of the first driver.
 16. Theamplifier of claim 6 wherein the amplifier is used to drive adistributed active transformer.